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 AWSAR Awarded Popular Science Stories
to drive its motion in opposite directions. How these opposite motors work together to bring about molecules to the right place at the right time is hotly debated. We have recently addressed this question in our manuscript published in “Current Biology” in May 2018.
In our study, we examined the motion of phagosomes in their early stages of phagocytosis. These Early Phagosomes (EPs) display bidirectional back and forth motion due to presence of both Kinesin and Dynein motors. To study motor function on EPs, we extracted them from immune cells using well-established protocols and made them walk on artificially constructed tracks. We analyzed their motion outside the cell using a special kind of microscopy called optical trapping. This technique provides tremendous amount of information as to how far motors can walk; the land forces exerted by each motor type their speed. Such experiments allow us to decipher properties of motors at a single phagosome level, a resolution that cannot be achieved when looking at an entire cell.
We investigated how could we explain back and forth motion of EPs? Do opposite motors depend on each other or do they pull against each other like in a tug of war? To make sense of how opposite motors behave on an EP, we specifically removed Dynein motors from the EP membrane. Surprisingly, upon Dynein removal, Kinesin neither performed better nor did it become worse. This suggested that both types of motors act independent of each other and do not require the opposite motor for their function.If motors function independently, what governs the choice of active motor when do horses pull and when do bullocks pull the cart? Is there a pattern these motors follow to bring about motion?
To answer this, we analyzed a number of events where pulling force was generated by Kinesin (horses) and Dynein (bullocks) motors. We focused on even pairs, for instance, a KK pair where Kinesin was followed by another Kinesin event, or KD pair where a Kinesin was followed by a Dynein event, DK pair where Dynein was followed by Kinesin
 Cartoon depicting a coin toss between Kinesin and Dynein motors on the phagosome
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